1. Field of the Invention
The present invention relates to a resist composition of a chemically-amplified which is used for processing of a semiconductor, a photo mask, and so forth, and responds to a high energy radiation such as an UV beam, a deep UV beam, an electron beam, an EUV, an X-ray, an excimer laser, a γ-beam, and a synchrotron beam, in particular to a resist composition of a chemically-amplified type used for a light-exposure by a beam exposure of a high energy radiation including an electron beam and a deep UV beam, and to a resist patterning process using the same.
2. Description of the Related Art
In recent years, as an integrated circuit progresses toward a higher integration, a further finer pattern formation is required, and a chemically-amplified type resist catalyzed by an acid has been mainly used in processing of a pattern with 0.2 micrometer or less. For this, high energy radiations such as an UV beam, a deep UV beam, and an electron beam are used as a light source, and especially an electron beam lithography used as a super fine miniaturization technology becomes indispensable also as a method for processing of a photo mask blank in preparation of a photo mask used for semiconductor manufacturing.
Generally, drawing by an electron beam is done by a beam of an electron beam, and in the case of a positive type without using a mask, a method in which a beam of an electron beam with a fine area is exposed sequentially on areas other than the areas to be remained in a resist film is employed. Accordingly, the operation is done in such a manner to drag on finely compartmentalized processing areas throughout the entire area, and thus the time is longer than a one-time exposure using a photo mask and thereby a high sensitivity resist is required in order not to sacrifice a throughput.
In addition, because of a longer drawing time, areas drawn in an early time and a later time tend to be different easily, and thus a temporal stability of an exposed area under vacuum is an important performance requirement item. Furthermore, in processing of a mask blanks which is an especially important application of it, there are some surface materials, like a film of a chrome compound including a chrome oxide that is laminated on a photo mask substrate, which tends to easily affect a pattern profile of a chemically-amplified type resist, and thus, in order to keep a high resolution and a form after etching, keeping a resist pattern profile in rectangular regardless of the kind of a substrate is also one of the important performance requirements.
Control of a resist sensitivity and a pattern profile as mentioned above has been improved by selecting materials used in a resist composition, a combination thereof, process conditions, and so forth. For example, in an early stage of the development, as to an acid catalyst to dissociate a protecting group of a resist polymer in a resist film of an chemically-amplified type, use of a super acid such as hexafluorcantimonic acid had been studied, and also a sulfonic acid having an increased acidity by a fluorine atom such as trifluoromethane sulfonic acid had been used, in order to obtain a rectangular profile and a high sensitivity.
In contrast, a camphor sulfonic acid which is a balky alklyl sulfonic acid not substituted by a fluorine atom had also been used from a relatively early time, in particular, in Japanese Patent Laid-Open Publication No. H6-266112, it is used with an aim to perform a catalytic reaction by using a relatively weak acid at high temperature.
On the other hand, in Japanese Patent Laid-Open Publication No. 2007-304528, a technology with which a line edge roughness is reduced, in an acrylic acid polymer protected by a tertiary alkyl group, by a combination of a highly acidic sulfonic acid containing a fluorine atom and a relatively low acidic alkyl sulfonic acid not containing a fluorine atom is disclosed, wherein use of a balky adamantyl sulfonic acid is disclosed as an example of the latter.
Furthermore, in a hyroxystyrene-type resist which is suitable for an electron beam lithography and the like, it is reported that a combination of a certain sulfonium and a benzenesulfonate having a substituent group is suitable as an acid generator such as shown in Japanese Patent Laid-Open Publication No. 2005-326833. Inventors of the present invention reported that a resist film may be made thinner by using a copolymer of hydroxystyrene and indene such as shown in Japanese Patent Laid-Open Publication No. 2008-95009 and Japanese Patent Laid-Open Publication No. 2007-132998.